Waternet, the public water cycle utility of Amsterdam and surroundings, has the ambition to operate climate neutrally in 2020. This requires a reduction of greenhouse gas (GHG) emissions of 48 kton CO2-eq. An inventory was made of measures to realize the target either in 2020 or in 2050. For all measures the effects on GHG emissions and on costs were determined. To comply with two core values of Waternet – economic effectivity and sustainability – the measures were prioritized based on CO2 effectivity, defined as costs per ton GHG emission reduction. To realize the target in 2020, 34 measures have to be implemented. The total investments are € 60 million, while the measures result in a decrease in yearly costs of € 5 million from 2020 onwards. In the case where the target has to be realized in 2050, 10 measures have to be implemented with a total investment of € 100 million and a decrease in yearly costs of € 16 million from 2050 onwards. As the cumulative cost savings in 2050 are € 50 million higher for the case where the target is already reached in 2020, and the uncertainty is lower, the realization of the target in 2020 is preferred.

INTRODUCTION

Waternet is the public water utility of Amsterdam and surroundings, responsible for all water related activities: drinking water supply, sewerage, wastewater treatment, surface water management, groundwater management, flood protection and control of the canals in Amsterdam. Some key characteristics are shown in Table 1. Because Waternet is in charge of all these activities, it can be seen as a water cycle company (Van der Hoek et al. 2011). Waternet has the ambition to operate climate neutrally in 2020. A climate neutral operation is defined as an operation without a net greenhouse gas (GHG) emission. This implies that additional measures are required to compensate for the inevitable GHG emissions, the so-called compensation measures.

Table 1

Key characteristics of Waternet

Drinking water supply   
  •  • drinking water production plants (nr)

 
  •  • drinking water supply (million m3/year)

 
87–88 
  •  • transport and distribution system (km)

 
3,105 
Wastewater treatment   
  •  • wastewater treatment plants (nr)

 
12 
  •  • capacity (people equivalents)

 
2,070,000 
  •  • sewage system (km)

 
3,968 
Surface water management   
  •  • surface area (ha)

 
70,000 
  •  • open water (ha)

 
9,500 
Groundwater management   
  •  • observation wells (nr)

 
3,000 
Flood protection   
  •  • primary dikes (km)

 
55 
  •  • secondary dikes (km)

 
570 
  •  • tertiary dikes (km)

 
471 
Control of Amsterdam canals   
  •  • bridges and sluices (nr)

 
76 
Drinking water supply   
  •  • drinking water production plants (nr)

 
  •  • drinking water supply (million m3/year)

 
87–88 
  •  • transport and distribution system (km)

 
3,105 
Wastewater treatment   
  •  • wastewater treatment plants (nr)

 
12 
  •  • capacity (people equivalents)

 
2,070,000 
  •  • sewage system (km)

 
3,968 
Surface water management   
  •  • surface area (ha)

 
70,000 
  •  • open water (ha)

 
9,500 
Groundwater management   
  •  • observation wells (nr)

 
3,000 
Flood protection   
  •  • primary dikes (km)

 
55 
  •  • secondary dikes (km)

 
570 
  •  • tertiary dikes (km)

 
471 
Control of Amsterdam canals   
  •  • bridges and sluices (nr)

 
76 

The ambition of Waternet to operate climate neutrally is driven by the policy targets of the City of Amsterdam, the Dutch government and the European Commission. The City of Amsterdam aims at a climate neutral municipal organization in 2015, 40% reduction of GHG emissions in 2025 compared to 1990, and 75% reduction of GHG emissions in 2040 (City of Amsterdam 2009). The European Commission recently published a communication in which a policy framework is proposed for climate and energy in the period from 2020 to 2030 (European Commission 2014). This includes the establishment of targets to reduce the GHG emissions by 40% compared to 1990, the increase of the share of renewable energy to 27% and the realization of 30% energy savings. These targets concern the whole European Union for the year 2030. Up until now the climate and energy targets for 2020 were 20% reduction in GHG emissions, 20% use of renewable energy and 20% energy savings. These targets were the basis of the objectives of the individual member states. The Dutch government also used these targets to develop the national policy. The importance of reducing GHG emissions is even more stressed when the IPCC's (Intergovernmental Panel on Climate Change) Fifth Assessment Report is taken into account (IPCC 2013). One of the conclusions is that continued emission of greenhouse gases will cause further warming and changes in all components of the climate system. Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions.

The emission of GHG by Waternet since 1990 is shown in Figure 1. The total emission decreased from 110,000 tons CO2-eq/year in 1990 to 48,175 tons CO2-eq/year in 2013. This reduction has been realized by energy savings, process optimizations (focusing on the use of raw materials and chemicals with less impact on GHG emissions), and by the use of renewable energy (Van der Hoek 2012). The figure shows that although an important reduction has been realized in the period 1990–2013, the target of a climate neutral operation in 2020 is difficult to reach when the pace of reduction is not increased. In a first inventory, performed in 2010–2011, the recovery of energy from the water cycle as a compensation measure was suggested (Mol et al. 2011; Van der Hoek 2012). This suggestion was based on an energy analysis of the Dutch water cycle by Hofman et al. (2011), in which it was concluded that creating an energy neutral water cycle by using the heat content or by making use of the organic load of wastewater seems realizable. A more detailed inventory for Waternet was performed in 2012–2013 (Van der Hoek et al. 2014). However, this more detailed inventory still focused on energy recovery from the water cycle, while economic considerations were not taken into account.
Figure 1

Reduction of greenhouse gas emissions by Waternet, period 1990-2013.

Figure 1

Reduction of greenhouse gas emissions by Waternet, period 1990-2013.

Economic considerations are especially important for Waternet. Waternet has three core values: economic effectivity – sustainability – customer orientation (Waternet 2015). Measures which reduce the GHG emissions or compensate the GHG emissions contribute to the core value sustainability, but may have a negative effect on economic effectivity as a result of more expensive processes, chemicals and raw materials.

The objectives of the study described in this article were threefold. The first objective was to create a detailed inventory of measures to operate climate neutrally in 2020, which go further than just energy recovery from the water cycle as in the previous inventories. The intention was to identify also measures related to other forms of renewable energy, process modifications in water treatment (both drinking water and wastewater), and use of alternative chemicals and raw materials. The second objective was to quantify the measures not only in terms of reduction of GHG emissions, but also in terms of finances, more specifically the required investments and the effects on yearly costs. The third objective was to develop a framework to prioritize all the measures based on the effect on GHG emissions and the financial implications.

METHODS

To identify measures, a workshop was organized for employees of Waternet. In this workshop all relevant disciplines were represented. The attendees were expected to propose measures to reduce GHG emissions without any restrictions. At the workshop all proposed measures were roughly estimated for their effect on GHG emissions. Subsequently, in a detailed study, all proposed measures were analyzed in-depth for their effect on GHG emissions and their effect on costs, and their realization periods were estimated.

GHG emissions were calculated based on the international Greenhouse Gas Protocol (World Resource Institute (WRI) & World Business Council for Sustainable Development (WBCSD) 2004). To determine the effect of greenhouse gas emissions on the climate footprint, the Intergovernmental Panel on Climate Change Global Warming Potential (IPCC GWP) 100a method (Solomon et al. 2007) was used. Within this method, only the environmental problem of climate change is evaluated and the results are expressed in CO2 equivalents.

In the Greenhouse Gas Protocol, emissions are divided in three scopes:

  • Scope 1: direct GHG emissions. Direct GHG emissions occur from sources that are owned or controlled by the company. This covers the emission of CO2 due to the use of fossil fuels, and the emission of nitrous oxide (N2O) and methane (CH4) as process emissions from wastewater and sludge treatment (Frijns 2012).

  • Scope 2: electricity indirect GHG emissions. Scope 2 accounts for GHG emissions from the generation of purchased electricity consumed by the company. Scope 2 emissions physically occur at the facility where the electricity is generated.

  • Scope 3: other indirect GHG emissions. Scope 3 emissions are a consequence of the activities of the company, but occur from sources not owned or controlled by the company. Indirect emissions result from, for example, extraction and production of purchased materials (chemicals, raw materials) and fuels, transport-related activities, waste disposal and use of sold products and services.

Scope 1 and scope 2 directly relate to the operations of Waternet and can be directly influenced by Waternet. Scope 3 concerns the emissions caused by chemicals, raw materials and services used by Waternet by the suppliers of these goods, and the emissions due to the use of products and services sold by Waternet. According to the Greenhouse Gas Protocol, scope 3 is optional. Accounting for scope 3 emissions need not involve a full-blown GHG life cycle analysis of all products and operations. In this study, for scope 3 positive effects on GHG emissions of measures initiated by Waternet, such as recovery of energy from the water cycle and reuse of biomass from the water cycle, were also taken into account and credited to Waternet to realize the aim of a climate neutral operation of Waternet.

Costs included operational costs (OPEX) and capital costs (CAPEX). To calculate capital costs from investment costs, two types of asset were defined: pipes and installations. For pipes a linear depreciation over 40 years was assumed, and for installations a linear depreciation over 15 years. In both cases an interest rate of 5% was assumed. Costs (OPEX) and investment costs were based on detailed cost calculations, use of the RoyalHaskoning-DHV cost calculator (RHDHV 2015) or expert judgment.

RESULTS AND DISCUSSION

In total 68 measures were collected and analyzed in detail for their effect on GHG emissions and costs. The measures partly fit in the existing systems and operations of Waternet, and partly require a total renewal of the systems and operations. The measures in the first category were placed in the relevant scopes, while the measures in the second category were placed in an additional category ‘from scratch’. Many measures require a realization period exceeding the year 2020. Therefore, 2050 was also taken as a realization horizon. Table 2 shows the results of this categorization. The results show that potentially it is possible to operate climate neutrally in 2020, as the reduction in GHG emissions exceeds the required 48 kton. Measures in scope 1 and scope 2, which can be directly influenced by Waternet, are not sufficient to operate climate neutrally in 2020. From the inventory it is clear that also measures have to be introduced from scope 3. In scope 3, especially the recovery of energy from the water cycle has a high potential. In 2050 recovery of energy from the water cycle exceeds 120 kton, which means that it covers more than 80% of all potential scope 3 measures (146.4 kton).

Table 2

Measures to operate climate neutrally per scope

Measures
 
Reduction GHG emissions (ton CO2)
 
Scope Number Time horizon 2020 Time horizon 2050 
29,725 34,675 
17 5,622 12,445 
25 43,704 146,374 
From scratch 18 43,713 194,248 
Total 68 122,764 387,742 
Measures
 
Reduction GHG emissions (ton CO2)
 
Scope Number Time horizon 2020 Time horizon 2050 
29,725 34,675 
17 5,622 12,445 
25 43,704 146,374 
From scratch 18 43,713 194,248 
Total 68 122,764 387,742 

The specific measures in scope 1, 2 and 3 are shown in Tables 3, 4 and 5 respectively. The tables show the reductions in GHG emission and the investment costs related to each measure, both for the time horizon 2020 and 2050.

Table 3

Scope 1 measures

Measure
 
Time horizon 2020
 
Time horizon 2050
 
Nr. Description Reduction GHG emissions (ton CO2Investment costs (€) Reduction GHG emissions (ton CO2Investment costs (€) 
S1-1 Sludge drying with solar energy or residual heat 4,582 3,490,000 9,164 6,980,000 
S1-2 Reduction CO2 emission from building heating by a Building Management System 144 55,000 144 55,000 
S1-3 Sealing sludge digestion tanks 3,861 200,000 3,861 200,000 
S1-4 Flue gas treatment of the combined power-heat generators in the furnace of the Amsterdam Waste-to-Energy plant 825 10,000 825 10,000 
S1-5 Burning of N2O from the waterline in the furnace of the Amsterdam Waste-to-Energy plant 10,508 4,000,000 10,508 4,000,000 
S1-6 Burning of CH4 from the waterline in the furnace of the Amsterdam Waste-to-Energy plant 9,437 3,000,000 9,437 3,000,000 
S1-7 Optimization of the nitrification in the wastewater treatment plants to reduce N2O production 186 150,000 371 300,000 
S1-8 Sealing sewers and use of recovered CH4 182 307,312,500 365 614,625,000 
Measure
 
Time horizon 2020
 
Time horizon 2050
 
Nr. Description Reduction GHG emissions (ton CO2Investment costs (€) Reduction GHG emissions (ton CO2Investment costs (€) 
S1-1 Sludge drying with solar energy or residual heat 4,582 3,490,000 9,164 6,980,000 
S1-2 Reduction CO2 emission from building heating by a Building Management System 144 55,000 144 55,000 
S1-3 Sealing sludge digestion tanks 3,861 200,000 3,861 200,000 
S1-4 Flue gas treatment of the combined power-heat generators in the furnace of the Amsterdam Waste-to-Energy plant 825 10,000 825 10,000 
S1-5 Burning of N2O from the waterline in the furnace of the Amsterdam Waste-to-Energy plant 10,508 4,000,000 10,508 4,000,000 
S1-6 Burning of CH4 from the waterline in the furnace of the Amsterdam Waste-to-Energy plant 9,437 3,000,000 9,437 3,000,000 
S1-7 Optimization of the nitrification in the wastewater treatment plants to reduce N2O production 186 150,000 371 300,000 
S1-8 Sealing sewers and use of recovered CH4 182 307,312,500 365 614,625,000 
Table 4

Scope 2 measures

Measure
 
Time horizon 2020
 
Time horizon 2050
 
Nr. Description Reduction GHG emissions (ton CO2Investment costs (€) Reduction GHG emissions (ton CO2Investment costs (€) 
S2-1 Side stream dosing of ozone in drinking water plants 13 321,530 13 321,530 
S2-2 Supply of drinking water to water company PWN by frequency controlled pumps 32 150,000 32 150,000 
S2-3 5 wind turbines of 3 MW 867 6,682,500 2,628 20,250,000 
S2-4 Shut down water conditioning at drinking water pretreatment plant Loenderveen 128 128 
S2-5 Installation of 100,000 solar panels 1,080 15,000,000 2,160 30,000,000 
S2-6 15 additional measures 2014 in the long term energy saving program 980 2,550,000 980 2,550,000 
S2-7 7 additional measures 2016 in the long term energy saving program 1,200 1,600,000 1,200 1,600,000 
S2-8 6 additional measures 2015 in the long term energy saving program 780 480,000 780 480,000 
S2-9 5 additional measures 2013 in the long term energy saving program 220 70,000 220 70,000 
S2-10 400 solar panels for heat production digestion and cooling panels 45 122,500 91 245,000 
S2-11 Efficiency improvement aeration wastewater treatment plants 124 1,500,000 124 1,500,000 
S2-12 Production drinking water and industrial water from wastewater effluent – – 3,151 3,624,000 
S2-13 Shut down water circulation between drinking water reservoirs 10,000 10,000 
S2-14 Use of DC instead of AC – – 192 50,000,000 
S2-15 Direct treatment of drinking water without dune passage – – 441 180,000,000 
S2-16 Replacement of small polder sewers by large polder sewers 27 25,000,000 54 50,000,000 
S2-17 Replacement of small sewage pumping stations by large sewage pumping stations 125 75,000,000 250 150,000,000 
Measure
 
Time horizon 2020
 
Time horizon 2050
 
Nr. Description Reduction GHG emissions (ton CO2Investment costs (€) Reduction GHG emissions (ton CO2Investment costs (€) 
S2-1 Side stream dosing of ozone in drinking water plants 13 321,530 13 321,530 
S2-2 Supply of drinking water to water company PWN by frequency controlled pumps 32 150,000 32 150,000 
S2-3 5 wind turbines of 3 MW 867 6,682,500 2,628 20,250,000 
S2-4 Shut down water conditioning at drinking water pretreatment plant Loenderveen 128 128 
S2-5 Installation of 100,000 solar panels 1,080 15,000,000 2,160 30,000,000 
S2-6 15 additional measures 2014 in the long term energy saving program 980 2,550,000 980 2,550,000 
S2-7 7 additional measures 2016 in the long term energy saving program 1,200 1,600,000 1,200 1,600,000 
S2-8 6 additional measures 2015 in the long term energy saving program 780 480,000 780 480,000 
S2-9 5 additional measures 2013 in the long term energy saving program 220 70,000 220 70,000 
S2-10 400 solar panels for heat production digestion and cooling panels 45 122,500 91 245,000 
S2-11 Efficiency improvement aeration wastewater treatment plants 124 1,500,000 124 1,500,000 
S2-12 Production drinking water and industrial water from wastewater effluent – – 3,151 3,624,000 
S2-13 Shut down water circulation between drinking water reservoirs 10,000 10,000 
S2-14 Use of DC instead of AC – – 192 50,000,000 
S2-15 Direct treatment of drinking water without dune passage – – 441 180,000,000 
S2-16 Replacement of small polder sewers by large polder sewers 27 25,000,000 54 50,000,000 
S2-17 Replacement of small sewage pumping stations by large sewage pumping stations 125 75,000,000 250 150,000,000 
Table 5

Scope 3 measures

Measure
 
Time horizon 2020
 
Time horizon 2050
 
Nr. Description Reduction GHG emissions (ton CO2Investment costs (€) Reduction GHG emissions (ton CO2Investment costs (€) 
S3-1 Use of calcite instead of garnet sand in drinking water softening 61 61 
S3-2 Use of 5 MW aquifer thermal energy storage in a data center 1,417 1,500,000 14,167 15,000,000 
S3-3 Use of surface water as a solar energy collector to regenerate aquifer thermal energy storage systems 2,521 2,688,000 25,210 26,880,000 
S3-4 Struvite recovery from wastewater 1,389 1,389 
S3-5 Use of thermal energy (heat) from wastewater to regenerate aquifer thermal energy storage systems 328 702,576 3,283 7,025,760 
S3-6 Use of 20,000 shower heat exchangers in households 809 1,500,000 6,470 12,000,000 
S3-7 Use of thermal energy (heat) from drinking water to regenerate aquifer thermal energy storage systems 219 500,000 1,094 2,550,000 
S3-8 Use of calcite garnets from drinking water softening in treatment of flue gas of the Amsterdam Waste-to-Energy plant 594 57,500 594 57,500 
S3-9 Use of thermal energy (cold) from surface to regenerate aquifer thermal energy storage systems 7,620 7,680,000 38,098 38,400,000 
S3-10 Use of CO2 from the conversion of biogas into green gas in drinking water treatment 1,343 360,000 6,716 1,800,000 
S3-11 Use of thermal energy (cold) from drinking water to regenerate aquifer thermal energy storage systems 661 900,000 3,307 4,500,000 
S3-12 Use of thermal energy (cold) from industrial water to regenerate aquifer thermal energy storage systems 496 500,000 2,480 2,500,000 
S3-13 Biogas production from glycol containing wastewater from Schiphol airport 634 50,000 634 50,000 
S3-14 Sludge destruction and expansion green gas production wastewater treatment plant Amsterdam West 1,000 5,000 
S3-15 Use of thermal energy (cold) from wastewater 46 500,000 231 2,500,000 
S3-16 Use of thermal energy (heat) from drinking water to regenerate aquifer thermal energy storage systems 405 500,000 2,025 2,500,000 
S3-17 Regeneration of an aquifer thermal energy storage at Schiphol airport with industrial water 10,000 10,000,000 8,000 8,000,000 
S3-18 Supply of industrial water without dune passage 2,417 110,000 4,833 220,000 
S3-19 Use of thermal energy from a drinking water transport main to recover an aquifer thermal energy storage in housing estate Diemen De Sniep 909 200,000 4,543 1,000,000 
S3-20 Use lime instead of sodium hydroxide in drinking water softening 8,542 200,000 8,542 200,000 
S3-21 Sustainable purchase of chemicals 1,000 50,000 1,000 100,000 
S3-22 Use of thermal energy (heat) from rainwater for room heating 470 2,400,000 2,349 12,000,000 
S3-23 Regeneration of activated carbon onsite 1,429 5,000,000 2,857 10,000,000 
S3-24 Use of grinders in households and production of CH4 -627 3,140,000 3,450 15,700,000 
S3-25 Use of iron containing membrane concentrate instead of FeCl3 in wastewater treatment plants 21 400,000 41 800,000 
Measure
 
Time horizon 2020
 
Time horizon 2050
 
Nr. Description Reduction GHG emissions (ton CO2Investment costs (€) Reduction GHG emissions (ton CO2Investment costs (€) 
S3-1 Use of calcite instead of garnet sand in drinking water softening 61 61 
S3-2 Use of 5 MW aquifer thermal energy storage in a data center 1,417 1,500,000 14,167 15,000,000 
S3-3 Use of surface water as a solar energy collector to regenerate aquifer thermal energy storage systems 2,521 2,688,000 25,210 26,880,000 
S3-4 Struvite recovery from wastewater 1,389 1,389 
S3-5 Use of thermal energy (heat) from wastewater to regenerate aquifer thermal energy storage systems 328 702,576 3,283 7,025,760 
S3-6 Use of 20,000 shower heat exchangers in households 809 1,500,000 6,470 12,000,000 
S3-7 Use of thermal energy (heat) from drinking water to regenerate aquifer thermal energy storage systems 219 500,000 1,094 2,550,000 
S3-8 Use of calcite garnets from drinking water softening in treatment of flue gas of the Amsterdam Waste-to-Energy plant 594 57,500 594 57,500 
S3-9 Use of thermal energy (cold) from surface to regenerate aquifer thermal energy storage systems 7,620 7,680,000 38,098 38,400,000 
S3-10 Use of CO2 from the conversion of biogas into green gas in drinking water treatment 1,343 360,000 6,716 1,800,000 
S3-11 Use of thermal energy (cold) from drinking water to regenerate aquifer thermal energy storage systems 661 900,000 3,307 4,500,000 
S3-12 Use of thermal energy (cold) from industrial water to regenerate aquifer thermal energy storage systems 496 500,000 2,480 2,500,000 
S3-13 Biogas production from glycol containing wastewater from Schiphol airport 634 50,000 634 50,000 
S3-14 Sludge destruction and expansion green gas production wastewater treatment plant Amsterdam West 1,000 5,000 
S3-15 Use of thermal energy (cold) from wastewater 46 500,000 231 2,500,000 
S3-16 Use of thermal energy (heat) from drinking water to regenerate aquifer thermal energy storage systems 405 500,000 2,025 2,500,000 
S3-17 Regeneration of an aquifer thermal energy storage at Schiphol airport with industrial water 10,000 10,000,000 8,000 8,000,000 
S3-18 Supply of industrial water without dune passage 2,417 110,000 4,833 220,000 
S3-19 Use of thermal energy from a drinking water transport main to recover an aquifer thermal energy storage in housing estate Diemen De Sniep 909 200,000 4,543 1,000,000 
S3-20 Use lime instead of sodium hydroxide in drinking water softening 8,542 200,000 8,542 200,000 
S3-21 Sustainable purchase of chemicals 1,000 50,000 1,000 100,000 
S3-22 Use of thermal energy (heat) from rainwater for room heating 470 2,400,000 2,349 12,000,000 
S3-23 Regeneration of activated carbon onsite 1,429 5,000,000 2,857 10,000,000 
S3-24 Use of grinders in households and production of CH4 -627 3,140,000 3,450 15,700,000 
S3-25 Use of iron containing membrane concentrate instead of FeCl3 in wastewater treatment plants 21 400,000 41 800,000 

Based on the effects on GHG emissions and the related costs, the measures can be prioritized in different ways. Two different approaches were considered. The first approach is based on reducing CO2 effectivity, in which CO2 effectivity is defined as costs per ton CO2 emission reduction. The costs concern the yearly costs including operational costs (OPEX) and depreciation costs (CAPEX). The second approach is based on reducing financial efficiency, in which financial efficiency is based on cost savings (OPEX + CAPEX) related to the investment costs. The core values of Waternet are economic effectivity, sustainability and customer orientation. To comply with the core values economic effectivity and sustainability, a prioritization was chosen based on reducing CO2 effectivity. By using CO2 effectivity as the basis for prioritization, both the core values of sustainability and economic effectivity are taken into account, while by using financial efficiency as the basis for prioritization only the core value economic effectivity is taken into account.

For the time horizon 2020 Figure 2(a) and 2(b) show the measures ordered by decreasing CO2 effectivity. Figure 2(a) shows the GHG emission reduction of each measure, the accumulated GHG emission reduction and the accumulated investments up to 2020. Figure 2(b) shows the investment costs and yearly costs of each measure, and the accumulated yearly costs up to 2020. To realize the target of climate neutral operation in 2020 (48 kton GHG reduction), 34 measures have to be implemented requiring a total investment of € 60 million (Figure 2(a)). Despite this high total investment, the effect on yearly costs is very positive: the 34 measures result in a decrease in yearly costs of about € 5 million from 2020 onwards (Figure 2(b)), due to the replacement of fossil fuel by renewable energy from the water cycle, selling of recovered energy from the water cycle to clients, reduction of the use of chemicals and raw materials, the use of alternative chemicals and raw materials, and reuse of waste materials. The simple payback time of the ‘Horizon 2020 case’ is 12 years.
Figure 2

(a) Measures until 2020: GHG emission reductions and accumulated investment costs. (b) Measures until 2020: investment costs and yearly costs per measure, and accumulated yearly costs.

Figure 2

(a) Measures until 2020: GHG emission reductions and accumulated investment costs. (b) Measures until 2020: investment costs and yearly costs per measure, and accumulated yearly costs.

In the case where 2050 is chosen as the time horizon to operate climate neutrally, it is possible to implement measures that require a longer realization time. As Figure 3(a) shows, in that case 10 measures are required with a total investment volume of € 100 million. Then the measures have a more pronounced positive effect on the yearly costs: they show a decrease of about € 16 million from 2050 onwards (Figure 3(b)). The simple payback time of the ‘Horizon 2050 case’ is 6 years.
Figure 3

(a) Measures until 2050: GHG emission reductions and accumulated investment costs. (b) Measures until 2050: investments costs and yearly costs per measure, and accumulated yearly costs.

Figure 3

(a) Measures until 2050: GHG emission reductions and accumulated investment costs. (b) Measures until 2050: investments costs and yearly costs per measure, and accumulated yearly costs.

The decrease in yearly costs which can be realized originates to a large extent from scope 3 measures, which in turn are for the major part related to energy recovery from the water cycle, which is partly sold to clients. This positive cost effect thus cannot be only credited to Waternet, but also to the clients who buy and use this renewable energy. In fact it has to be seen as cost savings for the whole society.

Table 6 compares the situations in which 2020 and 2050 are chosen as target years to realize a climate neutral operation, and in which the measures are prioritized based on CO2 effectivity. Although the number of measures to reach the target in 2020 is much higher, the total financial investments in 2020 are relatively low (€ 60 million compared to € 100 million in 2050). The ‘Horizon 2050 case’ yields higher yearly cost savings, but the total cost savings of the ‘Horizon 2020 case’ up to 2050 are calculated to be € 50 million higher. Based on the difference of € 50 million in 2050 in favor of 2020 as the target year, and higher yearly cost savings of € 11 million per year for the case where 2050 is chosen as target year (€ 16 million/year–€ 5 million/year), it will take 4.5 years before the ‘Horizon 2050 case’ exceeds the ‘Horizon 2020 case’ in total cost savings. For uncertainty reasons it seems financially more attractive to have 2020 as the target year to operate climate neutrally: uncertainties are higher in the long term and thus the realization of these higher total cost savings in the long term is more uncertain.

Table 6

Operating climate neutrally in 2020 or 2050: required measured and costs

  Horizon
 
2020 2050 
Number of measures 34 10 
Total investments (million €) 60 100 
Yearly investments (million €/year) 12 
Yearly cost savings (million €/year) 5 (2020 onwards) 16 (2050 onwards) 
Total cost savings until 2050 (million €) ∼165 ∼115 
  Horizon
 
2020 2050 
Number of measures 34 10 
Total investments (million €) 60 100 
Yearly investments (million €/year) 12 
Yearly cost savings (million €/year) 5 (2020 onwards) 16 (2050 onwards) 
Total cost savings until 2050 (million €) ∼165 ∼115 

Managing 34 projects up to 2020 is a large assignment for Waternet. Therefore, from a managerial point of view, it may be beneficial to start with those projects that have the largest absolute contribution to the reduction of GHG emissions (and not the highest CO2 effectivity) and to end up with measures with the lowest absolute contribution. From a practical point of view this manageability may be added to the prioritization criteria.

Another criterion that may be considered is the dependency on other partners to realize the GHG emission targets. For example, recovery of energy from the water cycle (scope 3) is attractive, but it can only be realized in close cooperation with partners who want to invest in the required equipment and who can use the recovered energy. In practice it appears difficult to establish this close cooperation. For that reason, focus on measures and projects in which Waternet is less dependent on partners may be beneficial. The drinking water treatment processes and wastewater treatment processes offer these possibilities, as already shown by Mohapatra et al. (2002) for the drinking water treatment processes of Waternet and by Klaversma et al. (2013) for processes in the whole Amsterdam water cycle.

CONCLUSIONS

An in-depth inventory of measures, covering all water-related activities of Waternet, showed that it is possible to operate climate neutrally in 2020. In 2020, a total of 68 measures, including energy recovery from the water cycle and reuses of biomass from the water cycle, result in a reduction of GHG emissions of 123 kton. In 2050 a reduction of 388 kton can be reached. This exceeds the required reduction of 48 kton.

Both an evaluation of GHG emission reductions and of accompanying financial effects is necessary to prioritize the measures. In order to be both cost effective and sustainable, prioritization of measures based on CO2 effectivity defined as total yearly costs per ton CO2 reduction, was shown to be a good approach.

Using this approach it can be concluded that 34 measures are required to reach the target of climate neutral operation in 2020 and 10 measures are required to reach the target in 2050. While total investments range from € 60 to € 100 million, total cost savings until 2050 are € 165 million for the 34 measures implemented from now until 2020 and € 115 million for the 10 measures implemented from now until 2050, making the option with 2020 as the target year financially more attractive.

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